The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
Not applicable.
(1) Field of the Invention
The present invention relates to coatings and more particularly to methods and apparatus for the application of coatings.
(2) Brief Description of the Prior Art
The prior art discloses a number of innovations related to the use of microwave, light and sound energy in improving painting or other coating processes.
U.S. Pat. No. 4,765,773 to Hopkins, for example, discloses a mobile paint application and microwave drying apparatus having a downwardly open hollow frame forming a microwave cavity movable over a surface on rollers. The interior cavity of the frame is coated with microwave absorbent material, as are the rollers. The frame in the front and rear conforms to the rollers with a certain gap and ends above the surface at a certain distance. Treads extend between the front and rear rollers on each side and have a thickness, which is greater than the gap and distance so as to create a circuitous path from the cavity which blocks microwave radiation. A paint spray nozzle is located in the cavity and applies paint to the surface. This paint is rapidly dried by a microwave generator, which is positioned in the cavity and directs radiation onto the wet paint.
U.S. Pat. No. 4,890,567 to Caduff discloses a robotically operated device using an ultrasonic transducer for the cleaning of a ship""s hull. The device may also be used for spraying paints or other chemicals on the sides of the ship""s hull. The device includes a housing having an open face adapted to confront the hull and apparatus disposed in the housing for impinging a flow of fluid through the open face onto the hull. An ultrasonic transducer is disposed in the housing for impinging a flow of ultrasonic energy through the open face onto the hull. Apparatus connected to the outside of the housing retains the housing on the ship""s hull and moves the housing on the hull. In an additional embodiment, apparatus for spraying paint or other chemicals on a ship""s hull is disposed in the housing.
U.S. Pat. No. 4,943,954 to Ostlie discloses a system and method for counteracting marine fouling of e.g., a vessel hull. Electro-mechanical vibration transducers are arranged in pairs adjacent to fixed nodal lines on the hull, and are driven in an inverted phase relationship in order to provide a water particle movement in a hull parallel direction right outside said nodal lines in addition to the hull perpendicular relative movements right outside said transducers. The invention also comprises a combination of the mechanical system above and a special surface coating which counteracts fouling from other organisms than those influenced by said water particle movement in the infra-frequency range.
U.S. Pat. No. 5,868,840 to Klein, II et al. discloses a spray gun for applying liquid spray coating, such as paint, to a surface incorporating a light source and detection system for analyzing the position of the spray gun relative to a work surface in order to optimize application of the coating to the surface. The light source is preferably in the form of a laser, which emits a beam of light toward the work surface. The laser is interconnected with the housing of the spray gun in a location over the spray gun handle so as not to effect the center of gravity of the spray gun. Optical sensors are reflected from the work surface, and the sensors are interconnected with a processor for providing the operator with a real time visual indication as to compliance with predetermined paint application criteria. In addition, information can be stored to memory and downloaded for subsequent analysis.
When spray painting an object, the paint will sometimes xe2x80x9cdripxe2x80x9d because it is applied to the surface unevenly. Paint may also tend to sag toward the bottom of a vertical substrate thus causing a thickness gradient in the paint layer.
A need, therefore, exists for an improved method of applying paint so as to avoid such features in the applied paint layer.
It is an object of the present invention to provide an economical and effective method for smoothing uneven features in the surface of the paint layer and reducing or eliminating thickness gradients in the paint layer.
This and other objects are met by the present invention, which is a method of coating a substrate. First, a liquid polymer based layer is applied to the substrate. Then, acoustic pressure is applied to the liquid polymer based layer to prevent irregular features and sag in the completed paint layer after drying.